Olefin mixtures containing vinyl, vinylidene and internal olefins of similar carbon number are difficult to separate by distillation based solely on the olefin type because vinyl, vinylidene and internal olefins having the same carbon number boil very close together This is generally the case when the olefins are made by a process capable of producing all three types of olefins. For example, the ethylene chain growth process using triethylaluminum followed by olefin displacement as practiced commercially can produce olefins containing from 4 up to 30 or more carbon atoms. The olefin type is mainly vinyl olefins, i.e. R--CH.dbd.CH.sub.2 wherein R is an aliphatic hydrocarbon group, but can contain lesser amounts of internal olefins, i.e. R--CH.dbd.CH--R wherein R is an aliphatic hydrocarbon group and vinylidene olefins, i.e. ##STR1## wherein R and R' are aliphatic hydrocarbon groups. When practiced to produce olefin mixtures containing up to 12 carbon atoms, the mixtures are predominantly, i.e. about 80 mole percent or more vinyl olefins. However when practiced to produce higher olefins, e.g. containing 14 or more carbon atoms, the amount of internal olefins and especially vinylidene olefins increases sharply such that in the C.sub.16-18 olefin range the olefin mixture will contain about 25-35 mole percent vinylidene olefins and 5-10 mole percent internal olefins. In some uses the vinylidene olefin content of olefin mixtures is not detrimental. However in some uses, the presence of vinylidene olefin decreases the value of the olefin mixture. For example, detergents can be made by reacting olefin mixtures with hydrogen sulfide to add hydrogen sulfide to the double bond forming a mercaptan. These in turn can be oxidized to form sulfonic acids which when converted to their salts are effective detergents. However vinylidene olefins react with hydrogen sulfide to form tertiary mercaptans which are very difficult to oxidize to sulfonic acids. Thus a need exists for a process for separating vinylidene olefins from a mixture containing vinyl, vinylidene and internal olefins which mixtures cannot be readily separated by distillation.